The present invention relates to apparatus for joining a plurality of elongate pieces of heat sealable material together to form a relatively large swimming pool cover or similar article.
When a swimming pool cover is formed by joining several elongate pieces of material together along an edge thereof, two such pieces are first joined along an edge and then successive pieces are added sequentially along an edge until eventually the entire cover is formed. Such covers are ordinarily formed of vinyl material which is relatively heavy and bulky, and as a result, handling of the cover as it is formed is a difficult process. The construction of a machine whereby such swimming pool covers can be formed mechanically has been a difficult problem. As a result, such covers have ordinarily been formed by using manual labor for handling the material, greatly increasing the cost of manufacturing such covers and rendering them economically unattractive.
Another problem with the swimming pool covers and similar items found in the prior art is that the seams between the elongate pieces of material used to form the cover are relatively weak. Such seams are ordinarily formed by overlying two pieces of elongate material so that their edges are aligned, and heat sealing the pieces together along the aligned edge. When the two pieces are unfolded to form the cover, a sharp 180.degree. turn or crease is required of one of the sheets. The stress caused by this crease can tear the sheet, and can cause it to come apart at the seam. As a result, the pool cover has weak spots at the seams which can cause it to fail prematurely.